1. Field of the Invention
The present general inventive concept relates to an electrophotographic image forming apparatus, and more particularly, to an electrophotographic image forming apparatus having a consistent image transfer contact region.
2. Description of the Related Art
An electrophotographic image forming apparatus is an apparatus that forms an image on a printing medium through a series of processes including a charging process to charge a drum or roller, an exposing process to expose the charged drum to light, for example, a developing process to attach toner to the exposed portions of the drum, a transferring process to transfer an image from the drum to a recording medium, a fusing process to fuse the image to the recording medium, and a cleaning process to clean the drum.
The image forming apparatus may include an image carrying body, such as a photoconductive drum, an exposing unit to expose a surface of the image carrying body, a developing unit to develop the exposed image carrying body with a developer, a transferring unit to transfer to a printing medium a visible image configured by the developer to be formed on a surface of the image carrying body by the developing process, and a fusing unit to fuse the visible image transferred to the transferring unit to the printing medium with heat and pressure.
Image-forming apparatuses may be classified into a multi pass type, which uses a single image carrying body or photoconductive drum, and a single pass type, which includes a plurality of image carrying bodies in a line along a transporting path of a printing medium to form a color image by a one-time passage of a printing medium.
In a conventional multi pass type image forming apparatus, an intermediate transferring belt faces the single image carrying body or photoconductive drum. After the single image carrying body is exposed and developed by each color of yellow, magenta, cyan, and black, a visible image formed on a surface of the single image carrying body is transferred to the middle transferring belt. By performing these processes by each color, that is, by repeating the charging, exposing, and developing processes four separate times, a final color image overlapped by the four colors is formed on the middle transferring belt.
The final color image on the intermediate transferring belt is transferred to a printing medium that passes between the intermediate transferring belt and a final transferring roller.
The final transferring roller may be movable between a separated position, in which it is separated from the intermediate transferring belt before the final color image is formed, and a contact position, in which it contacts the intermediate transferring belt to transfer from the intermediate transferring belt to a printing medium the final color image.
An arm that supports the final transferring roller contacts an inner frame portion of the image forming apparatus so that the contact position of the final transferring roller is regulated. The arm may have a bent shape, and the arm may be formed of a plastic material that is bendable.
However, since the contact position of the final transferring roller is regulated by a contact of the arm and the inner frame, a transferring contact region formed between the final transferring roller and a driving roller that drives the intermediate transferring belt fails to be uniform in a lengthwise direction, and the quality of an image is apt to be deteriorated.
Since the arm and the inner frame are substantially separated from the rotation shaft of the final transferring roller, the transferring contact region fails to be uniform.